DynamoDB Design

This system use DynamoDB.

Table Configs

Table Name: nishiki-table-prod-db
Deletion Policy: Retain (In develop environment, Delete)

note

In the development environment, the DB name is changed to the nishiki-table-dev-db.

Table Structure

Key

Partition Key is mostly ID of the entity. Sort key is normally, explains the type of data, if the data is about User, the sort key is USER. But this is relative.

Attributes

Name	Type	Note
UserId	String	UUID
UserName	String
EMailAddress	String
GroupId	String	UUID
GroupName	String
LinkExpiryDatetime	String	ISO 8601 date and time
InvitationLinkHash	String	This hash is generated from the Group ID and Expiry Datetime using the MD5 algorithm
ContainerId	String	UUID
ContainerName	String
Foods	List[Object]	Object Detail

Global Secondary Index (GSI)

UserAndGroupRelations

GSI Name: UserAndGroupRelationship
Projection Type: KEY_ONLY

Key	Attribute
PK	GroupId

info

This index is used for the access pattern of retrieving a list of users by the Group ID.

GroupAndContainerRelationship

GSI Name: GroupAndContainerRelationship
Projection Type: KEY_ONLY

Key	Attribute
PK	ContainerId

info

This index is used for the access pattern of retrieving a Group ID by the Container ID.

EMailUserRelation

GSI Name: EMailAndUserIdRelationship
Projection Type: KEY_ONLY

Key	Attribute
PK	EMailAddress

Non Key Attributes

• InvitationLinkHash

note

This GSI's PK is "ExpiryDatetime". Used for querying the expired Datetime.

InvitationHash

GSI Name: InvitationHash
Projection Type: INCLUDE

Key	Attribute
PK	InvitationLinkHash

Non Key Attributes

• LinkExpiryDatetime

Contexts

note

The {} means that the value inside it will be dynamic value.

User

PK: User ID (UUID)

SK	Detail	Attributes
User	User Data	UserName, EMailAddress
Group#{GroupID}	The group user belong to	GroupId

Group

PK: Group ID (UUID)

SK	Detail	Attributes
Group	Group Data	GroupName, Users
Container#{ContainerID}	Container Data	ContainerId
InvitationLinkHash	Invitation link's hash string	LinkExpiryDatetime, InvitationLinkHash

Container

PK: Container ID (UUID)

SK	Detail	Attribute
Container	Container Data	ContainerName, Foods

info

Container can be defined in the Group context using PK as group ID and SK as Container#{ContainerID}. While it makes the item structure more straightforward, it requires the use of a Global secondary Index(GSI) to retrieve container data using the container ID.

In this system, updating food operations are the most frequent, and in DynamoDB, writing operations are more than 5 times more expensive than reading. Using GSI for writing operations result in twice the cost which is not cost-effective. Hence, we prioritize cost efficiency and opted to separate the container from the group.

Foods

Food is the object.

{
    FoodId: string (UUID),
    Name: String,
    Unit: String | null,
    Quantity: Number | null,
    Category: String,
    Expiry: String (Datetime) | null,
    CreatedAt: String (Datetime)
}

Access Pattern

Access pattern name	Key (PK/SK)	How to Access	Detail	Context
GetUser	UserId / User	Get	Get a single user data	User
GetUser	UserId / Group#{GroupId}	Get	Check user's existence. return boolean.	Boolean (Primitive value)
GetUserByEMail	EMailAddress	Query against GSI	Get a single user's ID	User
ListOfUsersGroup	UserId / Group#	Query	List of groups user belonging to	User
GetGroup	GroupId / Group	Get	Get a group data	Group
GetGroup	ContainerId	Query against GSI	Get data of a group a container belonging to	Group
ListOfContainers	GroupId / Container#	Query	List of containers belonging to group	Group
ListOfUsersInGroup	GroupId	Query against GSI	List of users belonging to group	Group
GetContainer	ContainerId / Container	Get	Get a container data	Container
GetInvitationLink	InvitationHash	Query against GSI	Get an invitation link and related information	Group
GetInvitationLinkByGroupId	GroupId	Get	Get an invitation hash from the group ID	Group